Re: [PATCH for-5.0 v11 12/20] qapi: Introduce DEFINE_PROP_INTERVAL

[Auger Eric <eric.auger@redhat.com>]

Hi Markus,

On 12/12/19 1:17 PM, Markus Armbruster wrote:
> Eric Auger <eric.auger@redhat.com> writes:
> 
>> Introduce a new property defining a labelled interval:
>> <low address>,<high address>,label.
>>
>> This will be used to encode reserved IOVA regions. The label
>> is left undefined to ease reuse accross use cases.
> 
> What does the last sentence mean?
The dilemma was shall I specialize this property such as ReservedRegion
or shall I leave it generic enough to serve somebody else use case. I
first chose the latter but now I think I should rather call it something
like ReservedRegion as in any case it has addresses and an integer label.
> 
>> For instance, in virtio-iommu use case, reserved IOVA regions
>> will be passed by the machine code to the virtio-iommu-pci
>> device (an array of those). The label will match the
>> virtio_iommu_probe_resv_mem subtype value:
>> - VIRTIO_IOMMU_RESV_MEM_T_RESERVED (0)
>> - VIRTIO_IOMMU_RESV_MEM_T_MSI (1)
>>
>> This is used to inform the virtio-iommu-pci device it should
>> bypass the MSI region: 0xfee00000, 0xfeefffff, 1.
> 
> So the "label" part of "<low address>,<high address>,label" is a number?
yes it is.
> 
> Is a number appropriate for your use case, or would an enum be better?
I think a number is OK. There might be other types of reserved regions
in the future. Also if we want to allow somebody else to reuse that
property in another context, I would rather leave it open?
> 
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com> ---
>> hw/core/qdev-properties.c | 90 ++++++++++++++++++++++++++++++++++++
>> include/exec/memory.h | 6 +++ include/hw/qdev-properties.h | 3 ++
>> include/qemu/typedefs.h | 1 + 4 files changed, 100 insertions(+)
> 
> Subject has 'qapi:', but it's actually about qdev.  Please adjust the subject.
OK
> 
>> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
>> index ac28890e5a..8d70f34e37 100644
>> --- a/hw/core/qdev-properties.c
>> +++ b/hw/core/qdev-properties.c
>> @@ -13,6 +13,7 @@
>>  #include "qapi/visitor.h"
>>  #include "chardev/char.h"
>>  #include "qemu/uuid.h"
>> +#include "qemu/cutils.h"
>>  
>>  void qdev_prop_set_after_realize(DeviceState *dev, const char *name,
>>                                    Error **errp)
>> @@ -585,6 +586,95 @@ const PropertyInfo qdev_prop_macaddr = {
>>      .set   = set_mac,
>>  };
>>  
>> +/* --- Labelled Interval --- */
>> +
>> +/*
>> + * accepted syntax versions:
> 
> "versions"?
s/versions/version
> 
>> + *   <low address>,<high address>,<type>
>> + *   where low/high addresses are uint64_t in hexa (feat. 0x prefix)
> 
> "hexa" is not a word.
OK
> 
> I'm afraid I don't get the parenthesis.
I wanted to mention the 0x prefix was needed but as you mentionned below
it is not needed actually.
> 
>> + *   and type is an unsigned integer
>> + */
>> +static void get_interval(Object *obj, Visitor *v, const char *name,
>> +                         void *opaque, Error **errp)
>> +{
>> +    DeviceState *dev = DEVICE(obj);
>> +    Property *prop = opaque;
>> +    Interval *interval = qdev_get_prop_ptr(dev, prop);
>> +    char buffer[64];
>> +    char *p = buffer;
>> +
>> +    Snprintf(buffer, sizeof(buffer), "0x%"PRIx64",0x%"PRIx64",%d",
>> +             interval->low, interval->high, interval->type);
> 
> interval->type is unsigned.  Use %u, not %d.
OK
> 
>> +
>> +    visit_type_str(v, name, &p, errp);
>> +}
>> +
>> +static void set_interval(Object *obj, Visitor *v, const char *name,
>> +                         void *opaque, Error **errp)
>> +{
>> +    DeviceState *dev = DEVICE(obj);
>> +    Property *prop = opaque;
>> +    Interval *interval = qdev_get_prop_ptr(dev, prop);
>> +    Error *local_err = NULL;
>> +    unsigned int type;
>> +    gchar **fields;
>> +    uint64_t addr;
>> +    char *str;
>> +    int ret;
>> +
>> +    if (dev->realized) {
>> +        qdev_prop_set_after_realize(dev, name, errp);
>> +        return;
>> +    }
>> +
>> +    visit_type_str(v, name, &str, &local_err);
>> +    if (local_err) {
>> +        error_propagate(errp, local_err);
>> +        return;
>> +    }
>> +
>> +    fields = g_strsplit(str, ",", 3);
>> +
>> +    ret = qemu_strtou64(fields[0], NULL, 16, &addr);
> 
> Aha, the 0x prefix is actually optional.
> 
>> +    if (!ret) {
>> +        interval->low = addr;
>> +    } else {
>> +        error_setg(errp, "Failed to decode interval low addr");
>> +        error_append_hint(errp,
>> +                          "should be an address in hexa with 0x prefix\n");
> 
> "hexa" is not a word, and the 0x prefix is actually optional.
OK
> 
>> +        goto out;
>> +    }
> 
> I prefer
> 
>        if (error) {
>            handle error
>            bail out
>        }
>        handle success
> 
> over
> 
>        if (success) {
>            handle success
>        if (error) {
>            handle error
>            bail out
>        }
> 
> In this case:
> 
>        if (ret) {
>            error_setg(errp, "Failed to decode interval low addr");
>            error_append_hint(errp,
>                              "should be an address in hexa with 0x prefix\n");
>            goto out;
>        }
>        interval->low = addr;
OK
> 
> 
>> +
>> +    ret = qemu_strtou64(fields[1], NULL, 16, &addr);
> 
> Crash if @str doesn't contain ',', because the g_strsplit(str, ",", 3)
> yields { [0] = str, NULL }.
> 
>> +    if (!ret) {
>> +        interval->high = addr;
>> +    } else {
>> +        error_setg(errp, "Failed to decode interval high addr");
>> +        error_append_hint(errp,
>> +                          "should be an address in hexa with 0x prefix\n");
>> +        goto out;
>> +    }
>> +
>> +    ret = qemu_strtoui(fields[2], NULL, 10, &type);
> 
> Likewise, crash if @str contains only one ','.
> 
> I wouldn't use g_strsplit() here.  After
> 
>     ret = qemu_strtoui(str, &endptr, 16, &interval->low);
> 
> @endptr points behind the address.  So:
> 
>     if (ret || *endptr != ',') {
>         handle error ...
>         goto out
>     }
> 
>     ret = qemu_strtoui(endptr + 1, &endptr, 16, &interval->high);
> 
> and so forth.
> 
> Note that the if (ret || *endptr != ',') checks for two distinct errors.
> Distinct error messages might be more helpful.
OK I will revisit that.
> 
>> +    if (!ret) {
>> +        interval->type = type;
>> +    } else {
>> +        error_setg(errp, "Failed to decode interval type");
>> +        error_append_hint(errp, "should be an unsigned int in decimal\n");
>> +    }
>> +out:
>> +    g_free(str);
>> +    g_strfreev(fields);
>> +    return;
>> +}
>> +
>> +const PropertyInfo qdev_prop_interval = {
>> +    .name  = "labelled_interval",
>> +    .description = "Labelled interval, example: 0xFEE00000,0xFEEFFFFF,0",
>> +    .get   = get_interval,
>> +    .set   = set_interval,
>> +};
>> +
>>  /* --- on/off/auto --- */
>>  
>>  const PropertyInfo qdev_prop_on_off_auto = {
>> diff --git a/include/exec/memory.h b/include/exec/memory.h
>> index e499dc215b..e238d1c352 100644
>> --- a/include/exec/memory.h
>> +++ b/include/exec/memory.h
>> @@ -57,6 +57,12 @@ struct MemoryRegionMmio {
>>      CPUWriteMemoryFunc *write[3];
>>  };
>>  
>> +struct Interval {
>> +    hwaddr low;
>> +    hwaddr high;
>> +    unsigned int type;
>> +};
> 
> This isn't an interval.  An interval consists of two values, not three.
> 
> The third one is called "type" here, and "label" elsewhere.  Pick one
> and stick to it.
> 
> Then pick a name for the triple.  Elsewhere, you call it "labelled
> interval".
I would tend to use ReservedRegion now if nobody objects.

Thank you for the review!


Eric
> 
>> +
>>  typedef struct IOMMUTLBEntry IOMMUTLBEntry;
>>  
>>  /* See address_space_translate: bit 0 is read, bit 1 is write.  */
>> diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
>> index c6a8cb5516..2ba7c8711b 100644
>> --- a/include/hw/qdev-properties.h
>> +++ b/include/hw/qdev-properties.h
>> @@ -20,6 +20,7 @@ extern const PropertyInfo qdev_prop_chr;
>>  extern const PropertyInfo qdev_prop_tpm;
>>  extern const PropertyInfo qdev_prop_ptr;
>>  extern const PropertyInfo qdev_prop_macaddr;
>> +extern const PropertyInfo qdev_prop_interval;
>>  extern const PropertyInfo qdev_prop_on_off_auto;
>>  extern const PropertyInfo qdev_prop_losttickpolicy;
>>  extern const PropertyInfo qdev_prop_blockdev_on_error;
>> @@ -202,6 +203,8 @@ extern const PropertyInfo qdev_prop_pcie_link_width;
>>      DEFINE_PROP(_n, _s, _f, qdev_prop_drive_iothread, BlockBackend *)
>>  #define DEFINE_PROP_MACADDR(_n, _s, _f)         \
>>      DEFINE_PROP(_n, _s, _f, qdev_prop_macaddr, MACAddr)
>> +#define DEFINE_PROP_INTERVAL(_n, _s, _f)         \
>> +    DEFINE_PROP(_n, _s, _f, qdev_prop_interval, Interval)
>>  #define DEFINE_PROP_ON_OFF_AUTO(_n, _s, _f, _d) \
>>      DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_on_off_auto, OnOffAuto)
>>  #define DEFINE_PROP_LOSTTICKPOLICY(_n, _s, _f, _d) \
>> diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
>> index 375770a80f..a827c9a3fe 100644
>> --- a/include/qemu/typedefs.h
>> +++ b/include/qemu/typedefs.h
>> @@ -58,6 +58,7 @@ typedef struct ISABus ISABus;
>>  typedef struct ISADevice ISADevice;
>>  typedef struct IsaDma IsaDma;
>>  typedef struct MACAddr MACAddr;
>> +typedef struct Interval Interval;
>>  typedef struct MachineClass MachineClass;
>>  typedef struct MachineState MachineState;
>>  typedef struct MemoryListener MemoryListener;
> 
>